1. Field of Invention
This invention relates to a controller used to control processes; and more particularly, to a controller which has a high-grade function and a better man to machine interface function; which uses a full dot type display unit as a front operation panel on which a variety of control operation information can be selectively displayed; which is capable of selecting various control operations and panels in response to signals from operation keys; and which is capable of setting various parameters.
2. Description of the Prior Art
Conventionally, a single loop controller, equipped with a microprocessor, has been widely used in the field of process control. The single loop controller has certain advantages, such as a light engineering load, and a better operability, as compared to the distribution type control system (sometimes referred to as "DCS").
An example of such single loop controller is disclosed, for example, in Japanese Patent No. 57/57721 (1982), wherein the indicators for displaying information, such as process volume PV, set value SV, and control output MV, required to control the various functions, the operation keys for changing the set values, the operation keys for changing control modes, such as automatic control mode, and manual control mode, are arranged on the front panel, whereas the setting means for setting various parameters used to control calculations, for designating various functions, and for correction calculations, are provided on the side surface of the single loop controller.
Although such a conventional controller is capable of maintaining operability similar to the analog controller, there are problems with such conventional controller, such as, the measuring instruments must be removed from a rack, and the setting means, provided on the sides of the measuring instrument, must be operated so as to set the various parameters. Furthermore, since only a minimum number of indicators and operation keys, required to perform the control functions, has been provided on the front panel, the information required for other control operations, such as, the trend information for the process volume PV, must be recorded by use of a separate recorder.
Accordingly, it is evident that the prior art needs improvement.